1. Field of the Invention
The present invention relates to a suction roller for transporting flat material blanks, particularly such a suction roller for use in connection with a slit cover provided with passage holes. The suction roller according to the invention can particularly be used as a so-called blank separation roller in a label production machine. Applications in envelope production machines are also possible. Specifically, the suction roller can be used in window cutting stations, where window cutouts to be disposed of as waste must be separated from the envelope blanks that are to be processed further.
2. The Prior Art
It is known from DE 103 00 234 B3, in connection with label production, among other things, to use a suction roller as a blank separation roller. In this connection, rows of blanks (rows of label blanks) that run with an offset in the axial direction of the suction roller, in different tangential directions of the suction roller, are dispensed by the suction roller for further transport, in order to separate the rows of blanks, which usually engage into one another in nested manner for the purpose of minimizing scrap, from one another. For this purpose, the suction roller has a plurality of suction air bores, which are connected with suction channels that run axially in the suction roller. The suction air control ensures that adjacent rows of blanks are held against the mantle surface of the suction roller over angle stretches having different lengths.
An example of a specific embodiment of the suction channel system in the suction roller is known from DE 198 41 834 A1. FIGS. 3 and 4 of DE 198 41 834 A1 show suction channels that run in the axial direction. The suction channels stand in connection with suction air bores that open into the mantle surface of the suction roller.
Furthermore, so-called tube rollers having radial suction air bores are known, which stand in a suction connection with segment-shaped suction chambers configured in the interior of the tube roller, in order to produce the desired suction effect on the mantle surface.
In the case of label production, in particular, the case occurs, as a function of the production order, in each instance, that labels having a plurality of different geometries are to be produced. In order to constantly guarantee the desired separation of blanks, the suction raster image formed by the total of the suction air bores must therefore be changed as a function of the most varied geometries, i.e. formats of the label blanks.
With these known suction rollers, the raster distance between adjacent suction air bores, to which suction air can be applied independent of one another, lies on the order of magnitude of approximately 7 mm. This order of magnitude is not sufficient, in practice, to make controllable suction air bores available that lie so close to one another that the same suction roller can always be used as a blank separation roller, independent of the label format. Therefore, the production of different suction rollers as a function of format is necessary. This requirement leads to undesirable effort and expenditure in terms of costs, material, and storage.